ST. LOUIS -- While the St. Louis Rams play musical quarterbacks, the Arizona Cardinals continue to strum a winning tune.

Getting 356 yards and two touchdowns from quarterback Carson Palmer on Sunday, Arizona moved another step closer to an NFC West title with a 27-3 beating of St. Louis at Edward Jones Dome.

Palmer completed 26 of 40 passes, finding wide receiver J.J. Nelson for a 22-yard scoring strike less than five minutes into the game and hitting rookie running back David Johnson on a 10-yard touchdown pass to cap a 98-yard drive in the third quarter.

Those were part of a dominant 60 minutes for the Cardinals (10-2), who outgained the Rams 524-212 and amassed 29 first downs to St. Louis' nine in winning their sixth straight game.

"Pretty complete game," Arizona coach Bruce Arians said. "We finished our drives in the second half, got a great defensive effort and another great game out of our special teams. Can't find much to complain about."

Meanwhile, the Rams (4-8) couldn't find much to boast about, save for a 35-yard field goal by placekicker Zach Hocker in the third quarter. A shorthanded defense gave up a spate of big plays, and the offense again struggled to produce first downs, much less points.

Quarterback Nick Foles, starting for the second straight game in place of Case Keenum (concussion), completed just 15 of 35 passes for 146 yards and an interception.

"Defensively, our mindset was just to make Nick Foles beat us," Cardinals free safety Tyrann Mathieu said.

Foles was particularly ineffective on third down, hitting on just 1 of 11 for 9 yards. After the game, St. Louis coach Jeff Fisher announced that Keenum would start next week against Detroit.

"I have to be positive about it," Foles said. "I respect coach Fisher. There is so much I wish I could have done to change what happened today, but the sun will come up tomorrow and I'll work as hard as I can to help us win next week."

Rookie running back Todd Gurley rushed just nine times for 41 yards, 34 of those coming on his first run of the second half that set up Hocker's field goal. Otherwise, Arizona's front seven constantly whipped the Rams' injury-plagued offensive line, consistently meeting Gurley in the backfield.

"We're all disappointed and frustrated right now," Gurley said.

St. Louis could have made a game of it, though, had its defense been able to force a three-and-out after running back Kerwynn Williams fumbled a kickoff out of bounds at the 2-yard line.

Instead, Palmer found wide receiver Michael Floyd on a fade pattern, and he leaped over the tight coverage of cornerback Janoris Jenkins for a 31-yard gain. Seven plays later, Palmer fit a pass between two defenders to Johnson, and he waltzed into the end zone for a 17-3 lead at the 5:53 mark of the third quarter.

After the Rams went three-and-out for the third time, the Cardinals steamed 81 yards in seven plays to land the knockout punch. Williams raced 35 yards through a gaping hole up the middle with 1:30 remaining in the quarter to make it 24-3.

David Johnson, making his first start due to injuries that sidelined starter Chris Johnson and backup Andre Ellington, finished with 99 yards on 22 attempts. Williams added 59 on six carries.

Kicker Chandler Catanzaro added 33- and 29-yard field goals for Arizona, which could clinch the division title next week with a Thursday night win over Minnesota and a Seattle loss in Baltimore.

The Cardinals wrapped up a third straight 10-win season, but Arians wasn't of a mind to bask in that feat.

"Not right now," he said, "not on a short week. Big picture, there's still a lot left to accomplish."

NOTES: St. Louis CB Janoris Jenkins (concussion) left the game in the first quarter but returned. Jenkins then left the game a second time in the third quarter and didn't return. ... Rams TE Lance Kendricks (concussion) departed in the third quarter and wasn't able to return. ... Arizona TE Jermaine Gresham (shoulder) left the game in the third quarter and his status for Thursday night's game wasn't known.